Three Re(I) tricarbonyl complexes,
with general formulation Re(N^L)(CO)3X
(where N^L is a bidentate ligand containing a pyridine functionalized in the
position 2 with a thione or a thiazol-2-ylidene group and X is either chloro or
bromo) were synthesized and their reactivity explored in terms of
solvent-dependent ligand substitution, both in the ground and excited states.
When dissolved in acetonitrile, the complexes bound to the thione ligand underwent
ligand exchange with the solvent resulting in the formation of Re(NCMe)2(CO)3X.
The exchange was found to be reversible, and the starting complex was reformed
upon removal of the solvent. On the other hand, the complexes appeared inert in
dichloromethane or acetone. Conversely, the complex bound to the
thiazole-2-ylidene ligand did not display any ligand exchange reaction in the
dark, but underwent photoactivated ligand substitution when excited to its
lowest metal-to-ligand charge transfer manifold. Photolysis of this complex in
acetonitrile generated multiple products, including Re(I) tricarbonyl and dicarbonyl
solvato-complexes as well as free thiazole-2-ylidene ligand.